Alt. Replacement

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Dizzydean

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I was reading some of the threads on the guys replacing their alts with the bigger 90/120 units and saw all the extra upgrades with wiring that had to be done. So if going from the small 37 (50) to the 60 is the same amount of work required or would the be a direct bolt on. I would like to just go the next one bigger.
 
I would think that the factory wiring would not have a problem supporting the 60 amp alt but i am not sure what real gains you are looking for. In my opinion all of the wiring in these cars is rather undersized but that is just me. I upgraded to the newer 120 unit more for the improved charging at idle than the max output but i did take my ammeter out of the loop and upsized all of the other wiring.
 
What are you looking to do? If you're low charging or your alternator isn't putting out enough while at idle (ie lights dim, blinkers slow while at a stop light) then there are numerous threads in the electrical section with a ton of step by step instructions on how to find voltage drops.

The later stock "square back" alternators do put out more current at low idle than the earlier "round back" alternators. If you have a round back it could be part of your problem if you aren't getting enough juice at idle.
 
I installed a isolated field parts store replacement unit on mine years ago. It came with a output test that claimed 80 amps, but I don't what the test rpm was. I never had a problem with the higher output, but you run into problem when you do things like jump start another car with your car running. Or if you have a dead battery and you get jump started. In these situations your alternator will go max output and is much more likely to hurt your wiring(meaning fire).

Another factor I should mention is that my car is a 1965 and they use a bolt together connection at the bulkhead instead of the more common and failure prone slide together style.
 
If you install a 60A and do NOT have problems, I can assure you that you have "just been lucky." Even back "in the day" I had trouble with my own car, and the larger amp systems had what became known as "taxi/ fleet wiring." This is (dealer) option where the high current wiring was divorced from the troublesome bulkhead connector and ran through the bulkhead on larger gauge wire.

Please read this article from MAD. Even if you do not perform these modifications, this article gives a good insight into the trouble you face

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

The one really really BIG problem in these old girls over all others is the poor connections in the bulkhead/ firewall connector, which were never designed for that much current.
 
The first issue is with the ammeter. Run it into the +40 range for any length of time and you have a mopar bonfire. The second issue is +35 yr old wiring ( lots of resistance with corrosion ) and it being too small to adequately handle higher amperage. Sure, it may last a few months or even a few years, but it's trouble waiting to happen.
You'd have to upgrade the wiring ( or you should ) for the 50 amp alt anyway. Run the 90/120 amp one. You'll be able to run an electric cooling fan and all kinds of other stuff.
Just take your time and do it right
 
If your current alternator is keeping your battery charged, you don't need a bigger one. As others say, a bigger one could cause more problems than not. I also agree that if your lights are dim at idle, that indicates wiring and connector problems since everything should operate fine off the battery alone. The alternator's only job is to slowly recharge the battery. That said, the original round-back alternators have a weak output at idle, so if you spend a lot of time in stop & go traffic and drive short distances between starts, it may not keep your battery charged.
 
my 66 grenaded (quite literally) the shunt in the ammeter right in my driveway one day. bypassed the ammeter, but retained the accessory/fuse box/sign switch feed, wich was the original charge wire, tied it into a 60A firewall mounted manual reset circuit breaker and starter relay, with 4 GA. charge wire going from the Alt (78A square back) to the circuit breaker, and straight to the battery. never had a problem with lights or power since. I also installed a solid 4 GA ground wire to block, and a flat braided strap straight to the firewall.
 
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